Pyrrolo[2,3-d]pyrimidine compounds are inhibitors of protein kinases, such as the enzyme Janus Kinase 3 (JAK3) and are therefore useful therapy as immunosuppressive agents for organ transplants, xeno transplation, lupus, multiple sclerosis, rheumatoid arthritis, psoriasis, Type I diabetes and complications from diabetes, cancer, asthma, atopic dermatitis, autoimmune thyroid disorders, ulcerative colitis, Crohn's disease, Alzheimer's disease, Leukemia and other indications where immunosuppression would be desirable. The pyrrolo[2,3-d]pyrimidine compounds, pharmaceutical compositions thereof and methods of use are described in co-pending application Ser. No. 09/732669, filed Dec. 8, 2000, and assigned to the assignee of the present invention. The disclosure of said application is included in its entirety herein by reference thereto. Racemic mixtures of the pyrrolo[2,3-d]pyrimidine compounds are initially obtained whereas the individual enantiomers in substantially isolated pure form are preferred and at times required for drug use. It is possible to pre-ordain the stereochemistry of the compounds by use of stereospecific precursor compounds in the sythesis thereof. The methods of the present invention accordingly specifically relate to a method for the substantial chiral salt resolution of racemic mixtures of precursor compounds, used in the production of the separate enantiomeric forms of the pyrrolo[2,3-d]pyrimidine compounds.